1. Field of the Invention
The invention is generally related to a method for fabricating a pixel structure. More particularly, the invention relates to a method for fabricating a pixel structure having a color filter layer by using ink-jet printing for a color filter layer on thin film transistor array (COA).
2. Description of Related Art
With advantages of high definition, small volume, light weight, low driving voltage, low power consumption, and a wide range of applications, a liquid crystal display (LCD) has replaced a cathode ray tube (CRT) display and has become the mainstream display product in the next generation. A conventional LCD panel is formed by a color filter substrate having a color filter layer, a thin film transistor (TFT) array substrate, and a liquid crystal layer sandwiched between the color filter substrate and the TFT array substrate. In order to enhance the resolution of the panel and the aperture ratio of the pixel and to avoid an aligning error when the color filter substrate is bonded with the TFT array substrate, a technique of a color filter layer on TFT array (hence, color filter on array, COA) is provided nowadays.
Currently, a fabrication method for COA includes first forming an active device and a capacitor electrode line on the substrate, and thereafter forming a first passivation layer covering the active device and the capacitor electrode line. Next, after forming a light shielding layer and the color filter layer, a second passivation layer is formed covering the light shielding layer and the color filter layer. Thereafter, by performing a photolithographic process and an etching process, a contact hole exposing the active device as well as a hole corresponding to the capacitor electrode line are defined, and then afterwards a pixel electrode is formed.
Therefore, since the current fabrication method for COA requires many fabrication processes, there is still room for improvement.
Moreover, in order to further reduce costs for the next generation of LCD panels, in addition to COA, a lower cost ink-jet printing process is utilized to replace older fabrication methods of the color filter layer. However, in order to use the ink-jet printing process to fabricate the color filter layer, the light shielding layer is formed in the contact hole of the pixel structure and the surrounding area corresponding to the capacitor electrode line, thereby preventing ink flow thereto from the ink-jet printing process. However, forming the light shielding layer at the locations described above leads to a decrease in the aperture ratio of the pixel structure.